A general wheeled vehicle such as a motor vehicle has left and right front side frames at a front portion of a vehicle body. The left and right side frames extend to the front of the vehicle body from a dashboard lower panel, and a power unit such as an engine can be mounted on the left and right side frames.
The left and right side front side frames can be deformed plastically by means of a collision load (a frontal collision load) that is exerted on a front end of the vehicle body from the front. As this occurs, the power unit is displaced towards the rear of the vehicle body to strike the dashboard lower panel. To deal with this, it is required to enhance an occupant protection performance of protecting an occupant who is seated behind the dashboard lower panel in a passenger compartment. In order to enhance the occupant protection performance, patent literatures 1 to 5 disclose the known techniques in relation to a front structure of a vehicle body that restrain the dashboard lower panel from being deformed into the passenger compartment.
In a vehicle body front structure that is known through patent literature 1, a so-called transverse engine that is elongated in a vehicle's width direction is positioned between left and right front side frames. Left and right recess portions are formed on side surfaces of the left and right front side frames, respectively. The left and right front side frames are bent inwards in the vehicle's width direction by means of the frontal collision load to strike the engine. As a result of this, impact or collision energy in an initial stage of the collision is absorbed by the left and right front side frames and the engine.
In a vehicle body front structure that is known through patent literature 2, a so-called transverse power unit that is elongated in a vehicle's width direction is positioned between left and right front side frames. The power unit is mounted on the left and right front side frames. Left and right recess portions are formed on side surfaces of the left and right front side frames, respectively. The left and right front side frames are bent inwards in the vehicle's width direction by means of a frontal collision load to strike the power unit. As a result of this, impact or collision energy in an initial stage of the collision is absorbed by the left and right front side frames and the power unit.
A vehicle body front structure that is know through patent literature 3 is a similar technique to that disclosed by patent literature 2, and left and right brittle portions are formed on side surfaces of left and right front side frames. The left and right front side frames are bent inwards in the vehicle's width direction by means of a frontal collision load to strike the power unit. As a result of this, impact or collision energy in an initial stage of the collision is absorbed by the left and right front side frames and the power unit.
In the vehicle body front structure known through patent literatures 1 to 3, however, in case the collision energy is not absorbed completely in the initial stage of the collision, the power unit is displaced towards the rear of the vehicle body to strike the dashboard lower panel. There still remains room for improvement in restraining the dashboard lower panel from being deformed into the passenger compartment by the frontal collision in a more ensured fashion.
In a vehicle body front structure that is known through patent literature 4, left and right dampers that support left and right front wheels in suspension are provided on left and right front side frames, respectively. The left and right side frames are bent outwards in a vehicle's width direction by means of a frontal collision load to strike left and right front pillars via the left and right dampers. As a result of this, impact or collision energy in an initial stage of the collision is absorbed by the left and right front side frames and the left and right front pillars. There is no clear description on how a power unit that is mounted on the left and right front side frames acts. In the case of the power unit being displaced towards the rear of a vehicle body, there is the possibility that the power unit strikes a dashboard lower panel.
In a vehicle body front structure that is known through patent literature 5, a so-called transverse power unit that is elongated in a vehicle's width direction is positioned between left and right front side frames. The power unit is mounted on a subframe. The subframe is suspended from lower end portions of the left and right front side frames at a front end portion and a rear end portion thereof. In portions of the left and right front side frames, portions lying rearwards of the portions where the power unit is mounted, that is, left and right rearward portions are inclined inwards in the vehicle's width direction as the left and right front side frames extend towards the rear of the vehicle body. Left and right mounting brackets are provided on inner surfaces of the left and right rearward portion in relation to the vehicle's width direction. The subframe is detachably coupled to the left and right mounting brackets via left and right coupling portions.
Front portions of the left and right front side frames are collapsed by means of the frontal collision load. Because of this, the subframe and the power unit that are situated below the left and right front side frames are displaced downwards and rearwards. The power unit is displaced to strike the left and right coupling portions to thereby detach the left and right coupling portions from the left and right mounting brackets, respectively. As a result of this, the subframe is detached from the left and right mounting brackets. The power unit continues to be displaced rearwards and downwards by means of the frontal collision load and then strike the left and right mounting brackets. This collapses the left and right mounting brackets. In addition, the collapsing actions of the left and right front side frames has continued since a point in time when the frontal collision load started to be exerted on the left and right front side frames. Thus, the collision energy is absorbed.
Thus, in the vehicle body front structure that is known through patent literature 5, the collision energy is absorbed by collapsing the left and right mounting brackets by the rear-moving power unit. Absorbing the collision energy sufficiently requires the enlargement in size of the left and right mounting brackets where the subframe is coupled and increases the weight of the vehicle body. Moreover, the vehicle body front structure that is known through patent literature 5 is the configuration that is applicable only to the case where the left and right mounting brackets where the subframe is coupled are provided.